Windy weather

As I'm sure everyone has noticed, it's been quite windy at times over the past week in the Bay Area, along with southern California and much of the Southwest.  We had a classic set-up for a high wind event, similar to the event I described in the previous post, but much stronger.  Looking at the 500 mb pattern from last Thursday, we see a strong ridge over the eastern Pacific and a strong trough over the western U.S.  Imbedded in the trough is a strong shortwave over southern California, indicated by the tight gradient in heights.  This 500 mb pattern resulted in a strong offshore gradient at the surface - very strong winds blowing from the Great Basin westward across California.  Winds at higher elevations were easily above 50 mph with gusts well over 100 mph at the Sierra crest.  The winds are also enhanced locally through canyons, notably in the Los Angeles area, where most of the wind damage and power outages occurred.

As from the previous post, offshore winds also warm and dry as the air descends the Sierra down to sea-level at the California coast.  Temps reached the 70s on several days in the Bay Area.  In fact, outside of South Florida and South Texas, San Francisco was the warmest location in the country for a time on Friday - how often does that happen?!  The winds also scoured out the low-level moisture associated with the marine layer; you may have noticed how clear the skies were.  I noticed how clear Mount Diablo looked, which often appears hazy.  Finally, we can thank the dry offshore flow for the lack of dew on our car windows in the morning.

Looking ahead, aside from Monday, winds will be much lighter most of this week as the upper-level ridge over the Pacific slowly moves inland.  This will bring continued sunny skies with seasonably warm temps, but it will feel more humid again near the ocean and bays as the offshore flow weakens.  No rain in sight for the next week - certainly a dry start to December.